This invention relates to a fuel injection control for internal combustion engines and more particularly to an improved fuel injection control for engines embodying reed type check valves in the induction passages.
In many forms of internal combustion engine induction systems, there are employed reed type check valves in the intake passage. The use of such valves is commonly resorted to in two-cycle crankcase compression engines but this principle also has been applied to four-cycle engines even those having poppet valves. The function of the reed-type valve is to permit flow through the induction system toward the engine combustion chamber but to preclude flow in the opposite direction. This is almost essential in a two-cycle crankcase compression engine in order to permit the charge to be compressed in the crankcase chambers when the piston is moving downwardly in the cylinder bore. However, the principle is also utilized, as noted above, at times in four-cycle engines having conventional valves downstream of the check valves, to achieve a similar function.
One disadvantage with the use of the reed type check valve is that the fuel tends to continue to flow in the intake passage at a time when the reed type valve is closed. For example, with a carbureted engine and when the reed type valve is open, the fuel will be discharged front the discharge nozzles of the carburetor and will flow toward the reed type valve. However, the pressure differential which causes the valve to close may occur at a time when the fuel is still flowing. Thus, although the air flow may be stopped by the closure of the valve, the fuel because of its heavier density will continue to flow and will impinge upon the valve.
This phenomenon has a number of disadvantages. First, since the fuel which was intended for the combustion chamber is precluded from entering it, it may be necessary to enrich the mixture to provide the desired fuel/air ratio in the combustion chamber to make up the fuel which does not reach the combustion chamber. Although this fuel may flow into the intake passage upon the next opening of the reed type valve, its atomized state will not longer exist and there is an increased likelihood that the fuel will adhere to the walls of the intake passage and merely accumulate there. This accumulated fuel at times will also mix with the air flowing into the combustion chamber and thus the air/fuel ratio will become erratic.
These problems are not limited to carbureted engines. If a fuel injector is employed that is upstream of the reed type valve, the injected fuel also may impinge upon and condense on the reed type valve if it closes before all of the fuel has passed into the combustion chamber. Thus, the same detrimental effects aforenoted will occur with fuel-injected engines. The problem is more acute with fuel-injected engines, in fact. The reason for this is that the injection timing may be such that it occurs when the valve is closed or continues after the valve is closed. Since the injection cycle is not dependent upon air flow, the fuel flow will not be automatically stopped as the air flow decreases as it will with a carbureted engine.
It is, therefore, a principle object of this invention to provide an improved fuel injected internal combustion engine that employs reed valves in the intake passage and which will ensure against the adhesion of significant amounts of fuel on the reed type valve.
It is a further principle object of this invention to provide an improved fuel injection system and control for an engine having reed type valves in the intake system.